Sustainably produced biofuels are an alternative to fossil fuels and may help to alleviate the depletion of easily accessible fossil fuel stocks, such as cellulosic biomass, while avoiding fossil fuel-associated pollution and greenhouse gas emission, thus satisfying a rising demand for affordable energy in a sustainable way. The development of methods and oil-producing organisms suitable for the efficient conversion of carbon sources to lipids is prerequisite for widespread implementation of microbial biofuel production.